Currently, thermosetting composite parts are produced from material prepregged with resin in the form of strips or tapes (plies) in the non-polymerized state. These materials are generally stored at −18° C. in order to keep the resin at a degree of polymerization of less than 20%. The drape forming of the plies can be carried out manually or automatically and in particular according to the ATL (Automated Tape Laying) or AFP (Automated Fiber Placement) technique. This drape forming is carried out via a mechanical head equipped with means for supplying the plies and with pressure means, and optionally with means for cutting the plies and with heating means. The material is heated just before lay-up in order to increase the tackiness of the resin during the drape forming of the various plies one on top of the other. The application of pressure to the plies is carried out via a pressure roll.
The drawback of these types of techniques is that they require intermediate vacuum compactions to be carried out as soon as a few layers are draped, for example every 5 or 6 layers and that vary from one part to another. This intermediate compaction makes it possible to partly evacuate the air trapped between plies during the drape forming and to ensure correct holding of the various layers of the laminate to one another, by action of the tack.
In order to overcome this type of drawback, certain processes use a pressure roll equipped with a sonotrode (UTL or Ultrasonic Tape Laying technique) in order to reduce the amount of air trapped between the plies by virtue of the ultrasounds emitted. However, the use of such a process decreases the lay-up rate and therefore reduces the productivity, and does not completely prevent the need for intermediate compactions.
Intermediate compactions are very costly in terms of time, complicate the process and the device used, and do not eliminate the need for polymerizing the part under pressure in an autoclave in order to ensure a good performance of the material of the final part.